Network Interconnection: Technologies and Challenges

Posted on Dec 6, 2024 in Computers

Wide Area Networks

1.1 Network Interconnection

Interconnectivity (Internetworking) is the communication process between two or more networks.

Why is Network Interconnectivity Important?

  • Share Resources
  • Instant Access to shared databases
  • Insensitivity to physical distance and node limitations
  • Centralized management for strategic advantage

What Technical Challenges Exist?

  • Integration of equipment from different manufacturers
  • Varied architectures, platforms, operating systems, protocols, and media
  • Limitations in distance and packet size
  • Limitations in bandwidth and power

What Network Management Challenges Exist?

  • Configuration
  • Security
  • Reliability
  • Performance
  • Location
  • Isolation
  • Correcting and preventing failures
  • Planning ahead

How to Interconnect Networks

Networks are connected by telecommunications equipment known as interconnection equipment. Two or more separate networks connected to share data or resources form an internetwork. Linking LANs in an internetwork requires specific equipment designed to overcome interconnection obstacles without disrupting network operations.

Interconnection Equipment

LAN:

Hub, switch, repeater, gateway, bridge, access points.

MAN:

Repeater, layer 3 switch, router, multiplexer, wireless bridges, bridge, analog modem, ADSL modem, cable modem, DSU/CSU.

WAN:

Router, multiplexer, analog modem, DSU/CSU, satellite modem.

Modem

This peripheral has become indispensable, primarily for Internet and fax, but also for answering machine functions, switchboard capabilities, or connecting to the local network from a central office or company. The modem is used with analog lines, modulating and demodulating the digital signal from a computer into a waveform for analog lines.

Multiplexer

In telecommunications, a multiplexer receives and transmits multiple entries via a shared transmission medium. It divides the medium into multiple channels for simultaneous communication. A multiplexed signal requires demultiplexing at the receiving end. Types of multiplexing include:

  • Frequency Division Multiplexing
  • Time Division Multiplexing
  • Code Division Multiplexing
  • Wavelength Division Multiplexing

Switch

An electronic device for interconnecting computer networks, operating at layer 2 (data link layer) of the OSI model. A switch connects network segments, similar to bridges, moving data based on the destination MAC address.

Switches are used to connect multiple networks into one. Like bridges, they filter network traffic, improving LAN performance and security.

Hub

A network device that connects computers and retransmits received packets to all connected devices. Hubs are largely obsolete due to network traffic collisions.

MODEM, MULTIPLEXER, SWITCH, HUB

A hub is the central component of a star topology and can extend LAN size. While hubs don’t create WAN connections, they can increase the number of stations, but with design limitations.

Repeater

An electronic device that amplifies a weak signal for longer distances without significant degradation.

The term originated in telegraphy for electromechanical signal regeneration. It continues in telephony and data transmission.

  • Analog repeater: Amplifies any input signal (analog or digital).
  • Digital repeater: Amplifies, shapes, and/or retimes a digital signal for retransmission.
Characteristics of Process Signals

Signals degrade during transmission through attenuation. Repeaters allow signals to travel longer distances by operating at the physical layer of the OSI model, regenerating and forwarding the signal. A repeater takes a weak signal, regenerates it, and passes it to the next segment. Data packets and logical link control protocols must be identical in each segment.

Bridge

A device for interconnecting computer networks, operating at layer 2 (data link layer) of the OSI model. It uses a table of MAC addresses from each connected segment. When a node transmits data to another node, the bridge copies the frame to the other subnet.

The main difference between a bridge and a hub is that a hub forwards all traffic to all nodes, while a bridge only forwards frames belonging to each segment.

Bridges can be used to extend segment length, increase the number of computers on the network, reduce traffic bottlenecks, and divide a network.

Bridges operate at the data link layer of the OSI model, without access to higher-level information. They work at the MAC level and are sometimes called MAC-layer bridges. A MAC-layer bridge:

  • Checks source and destination addresses of each packet.
  • Constructs a routing table.
  • Forwards packets:
    • If the destination is not in the routing table, the bridge forwards the packet to all segments.
    • If the destination is in the routing table, the bridge forwards the packet to the corresponding segment (unless it’s the origin segment).
Operation

A bridge forwards packets based on the destination node address.

Benefits of a Bridge

Bridges offer all the features of repeaters with improved network performance.

Router

A router’s primary function is to determine if a packet’s recipient is on the local network or a remote one, using a “subnet mask.” The subnet mask is similar to an IP address and determines a computer’s group membership.

ROUTER OR ROUTER: A device connecting two LANs, controlling and classifying traffic between them. In complex systems, it acts as a security filter.

Routing Considerations
  • Static Routing: Predefined routes to the destination network.
  • Dynamic Routing: Routing information is exchanged periodically between routers, allowing routing based on current network topology. Dynamic routing requires additional resources for exchanging information and updating routing tables.